I took a quick walk through one of our restored wetlands last week. Most plants had finished blooming for the year, but in some recently-mowed patches, there were some scattered flowers of beggarticks (Bidens sp) and blue lobelia (Lobelia siphilitica). I knelt down to look more closely at some small bees I spotted crawling around on the lobelia flowers.
I saw one bee crawl in and out of one of the flowers, but for the most part, the bees (and a few flies) were all hanging around at the base of the flowers. As I watched, I saw one slide its long tongue into the flower. I couldn’t tell if it opened up a hole or just took advantage of one that was already there. Either way, it was apparently “stealing” nectar from the flower through a back window rather than entering politely through the front door.
I sent photos and questions to both Jennifer Hopwood and Mike Arduser, who are always generous about sharing their expertise with me. They both agreed with my interpretation, and Mike added some additional information. He said that blue lobelia flowers have slits in them that make this kind of nectar robbing pretty easy for bees.
It seems an odd strategy for a flower to make it easy for bees to steal nectar without providing any pollination services in return. Maybe the slits serve another purpose and the benefits outweigh the costs. Or maybe it’s just a random loophole that natural selection hasn’t yet closed. Regardless, blue lobelia plants tend to produce copious amounts of seed, so the flowers must get enough front door visitors to do the job.
In addition to the bees, there were a lot of flies hanging around the flowers too. Flies have pretty short tongues, and it didn’t look like any of them were sticking those tongues into the flower slits. Instead, they seemed to be feeding on the outside surface of the flower. Maybe nectar was seeping through those flower slits? Or maybe the bees were a little sloppy with their drinking and the bees were cleaning up after them? Whatever the reason, I saw at least as many flies as bees on the flowers, so there must have been some attraction.
I wish now that I’d spent more time examining the flowers, and that I’d brought one home with me so I could look at the slits under a scope. However, I hadn’t really planned to stop at the wetland, let alone to kneel down in the mud to look at bees stealing nectar from hapless flowers. Also, my neck was starting to throb a little from holding my head at an uncomfortable angle necessary to photograph the bees. Instead of sticking around to learn more, I took my camera, my muddy jeans, and my sore neck back to the truck and headed home.
Plains sunflower (Helianthus petiolaris) is an annual plant that responds quickly to bare ground in the Nebraska Sandhills. They pop up after fire, intensive grazing, pocket gopher activity or something else allows light to hit the soil. At times, they can be widespread, as they were the year after the 2012 drought. More often, they are found scattered about the prairie in patches of sparse vegetation. They have started to bloom in earnest over the last couple of weeks, adding beautiful accents to the summer prairie.
Last week, I spent an hour photographing sunflowers and the wide variety of small creatures I found hanging about on them. In just one hour, I spotted a pretty incredible abundance and diversity of invertebrates within an area smaller than my backyard. Sunflowers, especially annual sunflowers, are considered by some to be weeds, but these native wildflowers play really important roles in prairie ecology. Their seeds are extremely valuable as food sources for many wildlife species and their young leaves and flower buds/blossoms are quality forage for other species, including cattle. During this time of year, the abundant and accessible pollen and nectar of the flowers is what seemed to be attracting the invertebrates I saw. Here is a selection of photos displaying some of those sunflower visitors.
A variety of grasshopper, katydid, and tree cricket species are all commonly found feeding on the flower parts and pollen of sunflowers. Weevils, long-horned beetles, and other beetles are also frequently seen.
The abundance of herbivores, pollinators, and other insects on the flowers and vegetation of the sunflowers seemed to attract a number of predators as well, including robber flies, spiders, and assassin bugs.
I hope these photos, all taken from a small area and within a short time period, help illustrate the kind of resource annual sunflowers can be in the Sandhills. I’m sure many other wildflowers host similar numbers of invertebrates, but the height and conspicuous nature of sunflowers make it really easy to see and appreciate their value.
Annual sunflowers aren’t aggressive – they just take advantage of open soil and available root space. As vegetation recovers from whatever event caused it to become sparse, sunflower abundance diminishes…until they get another opportunity to pop back from seeds and make their contribution to the prairie ecosystem.
Wildflower season has officially returned to our area. I was out at my family’s prairie last weekend and found pussytoes (Antennaria neglecta), buffalo pea (Astragalus crassicarpus), and sun sedge (Carex heliophila) in bloom. Here in my yard, both the pussytoes and Carolina anemone (Anemone carolinianum) are blooming, along with the little blue-flowered weedy speedwell (Veronica persica) that always pops up around our garden and sidewalk edges. A few bees are moving around too, and there have been several kinds of flies visiting the pussytoes flowers. Here are a few photos of early spring flowers from this week.
Two weeks ago, I posted about Yellow Season in prairies. That annual phenomenon continues, and at our family prairie this week, stiff goldenrod was front and center. Pollinators and pollen-eating insects seemed to approve.
During the past two Mondays, I had the opportunity to help out with Prairie Plains Resource Institute’s Summer Orientation About Rivers (SOAR) program. It’s the best summer day camp I’ve ever been involved with, and my kids, my wife, and I have all enjoyed being part of it over many years. This year, I was tasked with talking to kids (about 8 kids at a time) about the value of biological diversity in ecosystems.
I needed an activity that would keep the kids engaged for about 15 minutes and send them away with an appreciation of why prairies need to have so many species in order to function well. With the help of my wife, I came up with a pretty good plan. Then I refined it a little each time I presented it to a new group of kids. It turned out well enough that I decided I’d share it here as well – I hope it helps you think about the same concepts I was trying to pass on to the kids.
I started off by talking about ordering food at a fast food restaurant. When you walk in, you go up to the counter and order food from the cashier. What happens if that cashier is sick that day? Do you just go home hungry? No, of course not – the restaurant has more than one person who can do that job, so someone else fills in and you still get to eat. Well, the same kind of thing happens in nature. Each organism in a prairie plays a certain role – it has a job to do – but if one species is unavailable (because of a disease outbreak, bad weather, etc.) other species can usually fill in and cover for it.
Next, I asked the kids for an example of a prairie species that plays an important role. Most of the time, someone said “bees”, which was perfect. If not, I provided that answer after discussing the ones they came up with. We talked briefly about the importance of pollination, the number of bee species found in many prairies (often 50-100 species), and that most of those bee species are “solitary bees”, meaning a single female trying to build and care for a nest of eggs. That female digs a tunnel in the ground (usually), lays an egg and then collects enough pollen and nectar to feed the larva until it becomes an adult. She seals the egg and food into a cell and then starts another cell on top of it.
I then showed them a couple sweat bees, and we talked about how bees that small couldn’t fly very far from their nest. Then I had them look at a circle of flags I’d put up around us (a circle with about a 50 meter radius) and told them that for some very small bees, a circle that size was basically their entire universe with their nest in the center. Within that circle, a female bee would have to go out every day and find enough food to both stay alive and provision her eggs.
Next I split the kids into groups of two or three and handed them a little bag with a wildflower in it. All of the flowers in the bags could be found within our circle of flags, but some were much more abundant than others. I told the kids they were solitary bees and their job was to spend the next five minutes counting the number of flowers (blossoms, not plants) within the circle that matched the one in their bag. Off they went!
After five minutes, I called them back in so we could talk about their search. Some of the kids struggled to find any flowers that matched their sample, while others came back with counts of between 100 and 200 blossoms. This led to a great discussion about the importance of plant diversity to bees. If a bee relied on only one plant species and it wasn’t very common within the “universe” around its nest, it would probably starve – especially because it would be competing with other pollinators for the pollen and nectar from those few flowers. Even if the bee’s flower species was really abundant, it might only bloom for a few weeks, so once it was gone, the bee wouldn’t have anything left to eat. However, if the bee’s universe contained lots of flower species it could feed from, the bee was likely to find enough food for itself and its eggs throughout its entire life.
To wrap up, I reinforced the point that bees rely on having lots of choices of plant species to feed on. If one plant species is unavailable, there are others that can provide the food the insects need. At the same time, most flowers also do best when there are lots of pollinator species available to visit them. In a prairie with a diverse community of bees, it’s less of a big deal when a few of those bee species are low in abundance because of weather or disease. Other bee species can cover for them and flowers still get pollinated.
Finally, I said that while we’d been talking about bees and flowers, biological diversity was important in many other ways as well. Many herbivores need lots of different kinds of plants so they can find high quality food all year round. A wide range of available prey species is important to predators. And so on. When a prairie, or other ecosystem, loses too many species, it’s just like a restaurant losing too many employees. At some point, there’s no one left to cover for someone who gets sick, and the system breaks down.
Two quick asides:
1. The fast food restaurant example I used with the kids was not my first idea. I actually started talking about bank tellers, and asked the kids what would happen if the bank teller was sick when you went to get money out of your account. However, my wife helpfully pointed out that most kids have probably never met a bank teller since so many people do their banking electronically or through ATM machines…
2. The circular “universe” around a solitary bee nest has been a really useful idea for me over the last several years. While the size of that circle varies quite a bit by bee species, the concept has changed the way I evaluate our prairie restoration and management. When I walk around our prairies, I often stop and think about what a solitary bee would experience if it were nesting there. If you’re in charge of a prairie, I’d encourage you to try it sometime – maybe it’ll be helpful to you as well.
Daisy fleabane (Erigeron strigosus) is considered by many people to be a weed. It’s a biennial with very pretty, albeit small, daisy-like flowers that flourishes when the dominant plants around it have been weakened. As a prairie manager, I’ve always appreciated daisy fleabane as an indicator that we’ve created conditions for new wildflowers (short- and long-lived) to insert themselves between the grasses in our sites.
Last Friday evening, I took my camera for a walk in a small prairie here in town and found quite a few daisy fleabane plants growing along the trail. I wasn’t the only one enjoying them – I saw numerous small bees and flies feeding on the pollen, and a few crab spiders hoping one of those pollinators waiting to ambush those same small pollinators.
The first crab spider I noticed slipped over the edge of the flower to hide when it spotted me coming toward it. I turned away to photograph something else nearby. When I looked back, the spider was back on the flower. I adjusted my position very slightly and the spider slipped back to its hiding place. Argh. Stubbornly, I decided I was going to photograph that spider if I had to wait all evening to do so. I didn’t have to wait quite that long, but it felt like it. I got my tripod positioned so that I could take the photo when/if the spider reappeared. Holding perfectly still, (with sweat running down my nose and mosquitoes feeding on my neck) I stayed in position for at least 5-10 minutes until the spider finally showed itself again. Got it!
A little further up the trail, I saw another crab spider that had caught a fly. I figured it too would make a run for cover when I got close, so I came in low and slow. I’m not sure it would have mattered – this spider showed none of the anxiety of the first one, and sat very still while I set up the tripod and waited for the breeze to pause long enough to get a good shot. Maybe this spider was too distracted by its meal to care about me (though that’s not been my experience in the past). I wasn’t sure whether to be grateful to the second spider for its cooperation or mad at the first one for all the mosquito bites on my neck.
I can understand why people might think of daisy fleabane as a weedy little plant, but its just filling an important role. When the grasses are weak, something has to take advantage of the temporarily available resources around and between them. There are numerous species that can do that, including a few that can cause real problems if they become established. Given the choices, I’m always happy to see the pretty little daisy flowers and the diverse tiny creatures they attract.
Some people have the mistaken impression that I know a lot about bees. Those who know me better understand that while I have a decent understanding of the ecology of bees and other pollinators, my identification skills are very rudimentary. Fortunately, I have become friends with Mike Arduser, formerly with the Missouri Department of Conservation, who has a comprehensive knowledge of bees in the Central United States. I sent Mike these photos a couple weeks ago and he generously identified the bee species for me, and provided a little background information as well.
According to Mike, the bee species I photographed on stiff sunflower (Helianthus pauciflorus) is a specialist feeder on sunflowers. It’s a common late summer bee in the Great Plains, but rare further east in the tallgrass prairies of Missouri, Illinois, etc. The bee nests in the ground and seeks out sunflowers for pollen and nectar.
During the morning when I photographed this species, I saw quite a few different bees. Most of them were males, and didn’t seem to be feeding on sunflowers as much as just hanging around the edges of the flowers – apparently waiting for a female to stop by.
I’ve only been learning about bees for a few years now. It’s amazing how many different species – and behaviors – I see, now that I’m looking for them. Before sending the photos to Mike, I was able to recognize these bees as being in (likely) the same species, and figured most of the ones I was seeing were males, based on their behavior. I still have much to learn, but paying attention to bees has certainly changed the way I see our prairies. As I wrote last fall, I’m definitely looking at our prairies through “bee goggles.” We’re not managing our prairie exclusively for bees, but they definitely factor in to our management decisions – not just because they are important themselves, but because promoting quality bee habitat is a great way to help ensure quality habitat for many other species as well.
Wasps are closely related to bees and ants, and some can be difficult to distinguish from their cousins. In this case, the long body makes me pretty sure this is a wasp (though body length is not always a good cue), but I don’t know what kind of wasp it is.
Most wasps are parasitoids, which means they capture and paralyze prey with venom from their stinger and then feed that still living, but paralyzed, prey to their wasp larvae. Usually, wasps specialize on a particular group of invertebrates (spiders, cicadas, grasshoppers, etc.). As with most insect groups, wasps are more abundant than you might think, and if you really start looking for them, you’ll find them all over. Most are not aggressive toward people and will sting only if you force them into it.
While the larvae of parasitoid wasps feed on paralyzed invertebrates, adults feed on pollen and nectar, and are pollinators for many plants. The one in the above photo, for example, has pollen stuck all over its face and body.
A guest post by Anne Stine, one of our Hubbard Fellows. All photos are by Anne.
I was scouting for native seeds in our sand pit restoration across from the crew quarters when I noticed a fascinating pollinator-plant interaction. This activity would’ve been best captured on video with a high quality zoom (which I did not have), but I was able to take pictures. Bumble bees, and only bumble bees, were fighting their way into great blue lobelias along the edge of our restoration. Meanwhile, their neighboring cardinal flowers were visited by butterflies exclusively. Why, and how, were these two closely related flowers so specialized with their pollinator partnerships?
First, let’s consider the great blue lobelia (Lobelia siphilitica). The architecture of this flower insures that only burly bumble bees can gain access to the pollen and nectar. Some other insects “cheat” and chew holes in the flower to by-pass the petal-gate, but bumble bees are their primary visitors. Watching the bumble bees pry open the flowers was entertaining. First, they climb onto the flower’s extending ‘tongue’. Then, they push aside the two top petal ‘lips’ and dunk themselves head first into the flower. Their front half is completely inside the blossom. Only their bottoms and back legs stick out. They clamber up the stalk, climbing from flower to flower until they reach the top, and then they fly off to visit a neighboring plant. Because great blue lobelia seems to grow in patches, this is an efficient operation for both bee and blossom. The bees act drunk on nectar, and the flowers are practically guaranteed a thorough pollination.
Conversely, cardinal flower (Lobelia cardinalis) is traditionally considered to be a ‘hummingbird-specialist’ plant. We are just outside the range of the ruby throated hummingbird here on the Platte River Prairies. Instead, butterflies with their long tongues seem to have taken over the majority of the nectaring and pollination duties. Or perhaps cardinal flowers in this part of Nebraska predominately self-pollinate. At any rate, bees weren’t the major customers on cardinal flowers. Cardinal flowers were visited by butterflies.
How strange that these two wetland con-generics, great blue lobelia and cardinal flower, could grow in intermingled patches and still rely on totally distinct pollinator communities. Nature is weird and wonderful.
This monarch had the choice between blue lobelia and cardinal flower. She chose cardinal flower. So did all the other butterflies.